The present invention relates to a novel implant material excellent in biocompatibility, stability in living body and mechanical properties, comprising a metallic material and a layer of a thermosetting resin or a layer of a composition comprising the thermosetting resin and hydroxyapatite, the layer of the thermosetting resin or the layer of the composition being formed around the metallic material.
In recent years, with the development of biotechnology, implant techniques which implant artificial material processed in a shape of joint or radix dentis into bone tissue of human body have been highlighted.
As the artificial material used in the implant technique, metallic materials such as alloys of cobalt and chromium, titanium, tantalum and the like, and ceramic materials such as hydroxyapatite, zirconia, alumina, glassy carbon and the like have hitherto been known. However although the metallic materials are excellent in mechanical strength, they are poor in biocompatibility and some of them are injurious due to the eduction of metal ions. On the other hand, the ceramic materials are excellent in biocompatibility, however, they are still poor in mechanical properties.
Namely, the conventional artificial materials have one or more of demerits concerning toxicity, compatibility bones, mechanical properties or durability and accordingly, they can not be said to be the satisfactory implant materials. Accordingly, trials of combining different materials have been carried out in order to settle the above-mentioned problems.
For instance, Japanese Patent Application Laying-Open (KOKAI) No. 53-28997 (1978) discloses, as an implant material in which a metallic material and another material have been integrated into one body, the implant material made by forming a melt-ejected layer of powdery ceramic or powdery hydroxyapatite on the surface of a metallic material. Such an implant material is expected from the view point of making the most of both the biocompatibility of hydroxyapatite and the mechanical strength of metallic material, however, cracks are apt to be formed in the melt-ejected layer due to the difference of thermal expansion between the metallic material and the melt-ejected material layer, and eduction of metal ions from the thus formed crack is feared.
In addition, Japanese Patent Application Laying-Open (KOKAI) No. 57-156757 (1982) discloses an implant material made by coating the outer surface of a metallic material with a composition singly formed by a thermoplastic polymer such as polysulfon, high density polyethylene, poly(methyl methacrylate) and the like, or formed by adding from 20 to 30% by weight of an inorganic material such as calcium phosphate, hydroxyapatite and the like to the thermoplastic polymer.
However, the thermoplastic polymers are insufficient in the adhesion to the metallic material, the stability in living body, the osteogenesity and the mechanical properties and accordingly, they are not practically reliable.
As a result of the present inventor's studies for developing an implant material which is excellent in the adhesion to the metallic material, the osteogenesity, the mechanical properties and the feeling on actual use thereof and is reliable on practical use, he has found that the implant material obtained by forming a layer of thermosetting resin which is favorable in biocompatibility and stability in living body, around the outer surface of the metallic material solves the demerits of the conventional implant materials and based on the finding, the present invention has been attained.